Cylindrical thin-walled header with constant cross sections and thin-walled header with variable cross sections have been used in molten-salt receiving solar absorption panels, to which solar absorption pipes are connected by means of sleeves or nozzles that have previously been machined and subsequently welded. In some cases, the nozzles have been directly extruded from the collector. Such embodiments have been disclosed in U.S. Pat. No. 6,736,134-B2 and its counterpart WO 03/021159 A2, and in US2009/250051 A1 and its counterpart ES-2263394-B1, respectively.
Some of the constructions of this kind subject the areas that join the header body to the solar absorption pipes to high thermal strains. These thermal strains are caused by rapid temperature changes in the molten salts flowing through the header due to the passage of clouds over the heliostat field of a solar plant. These thermal strains due to abrupt temperature changes may be attenuated by placing jackets or other thermal protection at the nozzles that join the solar absorption pipes to the header. However, these protections have geometries which are complex regarding manufacturing and difficult to assemble. Without this protection operational lifetime of the plant is extremely short.
On the other hand, this header requires a minimum passage cross section so as to uniformly distribute the flow of salts or other transmission fluid through all solar absorption pipes connected to the header, at a lowest-possible pressure loss. It is however well know that flow of molten salt or transmission fluid is not uniform along the collector and that such variable flow distribution will depend on the arrangement of the connections on the header of the pipe or pipes feeding it and of the solar absorption pipes that distribute the salts or transmission fluid.
In cylindrical header having constant cross sections and fed basically by their central portions, speed of the transmission fluid becomes substantially reduced in the lateral areas as the fluid has been distributed through the solar absorption pipes that connect to the central portion of the header, thereby causing severe thermal strains in the nozzles that join the solar absorption pipes connecting with the collector's side portions.
This design involving a cylindrical header having a constant cross section does not optimize the combination of thermal strains generators by transiently-passing clouds with the mechanical strains that the header must also absorb as a container which stands under pressure in these portions that are remote from the collector's feeding pipes, therefore involving that its main body requires wall thicknesses that are larger than desired, which in turn again are adverse for the thermal strains as derived to the nozzles joining the header to the pipes.
In the design of headers having variables cross sections and thin walls, the goal is to provide an improved header design that is suitable to be used in solar receiver panels for molten salts or any other transmission fluid, by more efficiently stand the thermal strains experienced by the nozzles joining the header to the solar absorption pipes.
It is thus one main object of the present invention to provide a header design for use in molten-salt or other transmission fluid solar receiver panels which deals more effectively with the thermal strains experienced at the nozzles joining the header to the solar absorption pipes without the need for using complex and expensive thermal protection devices.
It is another object of the present invention to provide a header design for use in molten-salt or other transmission fluid solar receiver panels which allows using the same concept of a nozzle joining the header and solar absorption pipe, for all thereto-connected tubes including those areas of both high flow and low flow of salts or other fluids, of the header, thereby achieving the resulting advantages regarding manufacturing and costs.